[Parthenogenetic development of murine ova activated by heat shock]

The effects of heating oviducts up to 37-42 degrees on the ovulated mouse eggs have been studied. The heating of oviducts at 39.5 degrees for 7 min resulted in 85% activation. The subsequent increase in temperature did not raise the incidence of activation but led to the formation of micronuclei and other pathological changes in the pronuclei. The heating of oviducts at 39.5 degrees for 14 min demonstrated marked changes in heat resistance, which were dependent on the postovulatory age of eggs. The freshly ovulated eggs were characterized by a low resistance and were not activated by the heat shock. If the oviducts were first heated and then cooled, and again heated, most eggs were activated and their in vitro development was the best of all experimental series. The mechanisms of egg activation by heating are discussed.